(Supported in part by NIH DEO R298586 to D. Steflik). This long-term comparative project uses the HVEM/IVEM to obtain 3-D structural information on the biological characteristics of dental implant systems which are representative of currently used implants. The work is based on an in vivo dog model which permits macroscopic and microscopic evaluations of how the oral tissue (bone, connective tissue and epithelium) responds to endosteal dental implants at various time periods. HVEM of thick sections has been shown by Dr. Steflik to be the method of choice for studying bone-dental implant interfaces. Steflik, D.E., R. S. Corpe, F.T. Lake, A.L. Sisk, G.R. Parr, P.J. Hanes and K. Buttle. (1997) Composite morphology of the bone and associated support-tissue interfaces to osseointegrated dental implants: TEM and HVEM analyses. Internat. J. Oral Maxillofacial Implants 12:443-453. Steflik, D.E., F.T. Lake, A.L. Sisk, G.R. Parr, P.J. Hanes and K.F. Buttle. (1997) Transmission electron microscopy of the interfacial tissues apposing osseointegrated implants. J. Dent. Res., 75:400. Steflik, D.E., T.F. lake, A.L. Sisk, G.R. Parr, P.J. Hanes and K.F. Buttle. (1997) Tissue interfaces to dental implants: Electron microscopic analyses. Fifth World Biomaterials Congress, May 29-June, 2, 1997, Toronto, Canada. Steflik, D.E., R.S. Corpe, F.T. Lake, T.R. young, A.L. Sisk, G.R. Parr, P.J. hanes and D.J. Berkery. (1997) Ultrastructural analyses of the attachment (bonding) zone between bone and implanted biomaterials. J. Biomed. Mater. Res. (in press).